* tests/defs.m4sh (func_get_config): Build egrep regex to speed

* tests/defs.m4sh (func_get_config): Build egrep regex to speed
up extracting several variables at once.  Use it to extract all
default variables at once.  Also extract build_alias and
host_alias from the libtool script.
(func_configure_nofail): Use build_alias and host_alias for
--build and --host, respectively.  Pass each if nonempty.
* tests/testsuite.at: Pass --build if build_alias is nonemtpy.
* tests/quote.test: Extract ECHO and wl at once.